1. Field
The present disclosure relates to a curable silicone resin composition containing an inorganic oxide and an optical member using the same.
2. Description of Related Art
Light emitting diode (LED) devices commonly feature LED chips mounted therein. The LED chips are encapsulated within a transparent resin, such as an epoxy resin or a silicone resin, to protect the LED chips.
As epoxy resins for the encapsulation of LED chips, bisphenol A type epoxy resins having a phenyl group and cresol novolak type epoxy resins have been used. When these epoxy resins are used as encapsulation resins, radicals that may be generated by heat or light cause the encapsulation resins to be subject to oxidation degradation, resulting in yellowing. Thus, hydrogen-added epoxy resins having improved yellowing resistance may be used as epoxy resins for the encapsulation of LED chips. However, even when such epoxy resins are used as encapsulation resins, if the level of energy emitted by the LED chips increases due to the LED devices operating at short wavelengths and relatively high luminance, the encapsulation resins are still yellowed and thus reduce the luminance of the LED device.
Meanwhile, dimethyl silicone resins may also be used as silicone resins for the encapsulation of LED chips. Dimethyl silicone resins have excellent heat resistance and light resistance, as compared to epoxy resins. However, refractive indexes nD of dimethyl silicone resins are relatively low (about 1.4), and are less than those of LED chips. Thus, when light emitted by LED chips is received in dimethyl silicone resins at an angle less than the critical angle, the light is totally reflected at the interface with the dimethyl silicone resin. When total reflection occurs, the extraction efficiency of the light deteriorates, thereby reducing the luminance of the LED devices.
For this reason, in order to provide silicone resins having a relatively high refractive index, a method of using a silicone resin having a phenyl group is being examined. However, since phenyl groups absorb ultraviolet rays and thereby generate radicals, such encapsulation resins are subject to oxidation degradation when the LED devices operate at short wavelengths and will thus be yellowed, similar to the case of epoxy resins. Furthermore, when silicone resins having phenyl groups are used in high-power LED devices having an output of 1 W or more, the high-power LED devices deteriorate due to the heat that is generated.
In addition, in order for silicone resins to have a relatively high refractive index while maintaining heat resistance and light resistance, a method of mixing inorganic oxide particles, such as zirconia and the like, which have excellent thermal stability and relatively high refractive indexes, with a silicone resin is being considered.